Directly tunable lasers, such as e.g. distributed feedback (DFB) lasers suffer from self-heating induced wavelength drifts during burst-mode operation. In signal processing, this drift results in signal degradations when signals generated by these lasers are passed through narrowband wavelength filters at the receive side, e.g. at the optical line termination (OLT) in a time and wavelength division multiplexed passive optical network (TWDM-PON). This issue also applies to ADFB lasers, so that conventional ADFB lasers are not useable in networks with filter widths in the order of 50 GHz or less.
A number of generic mitigation techniques that are applicable to ADFB lasers have been proposed so far, e.g. applying accelerated heating, elevated subthreshold bias current or operation at low output powers. However, in order for these mitigation techniques to be efficient, the respective ADFB laser would need to be driven in a non-optimal point of operation, resulting in system penalties due to e.g. lower power or degraded eye openings.
Thus, there is a need for improved self-heating mitigation techniques applicable to ADFB lasers.